Advanced Animal Breeding Programs Prior to Genomic Selection

All animal breeding programs are based on the principles of quantitative genetics. Advanced animal breeding programs can be divided into two groups: within-breed selection and programs based on crossbreeding among different breeds. Breeding programs based on crossbreeding are the norms for beef cattle, poultry, and swine. Crossbreeding programs can be further divided into those programs that are based on crossing two, three, or four breeds. This chapter describes the basic principles used to evaluate selection within a breed. Then it applies these principles to the specific problems related to dairy cattle breeding and the major breeding schemes that have been applied or proposed. The chapter also focuses on the advantages and limitations of crossbreeding programs, especially as related to marker-assisted selection (MAS). With respect to crossbreeding programs, it is possible that genomic selection might help to limit some of the guesswork involved in exploiting heterosis.